1. Field of the Invention
This invention relates generally to a guideway and levitation system for transport vehicles, and more particularly concerns an electromagnetic induction and levitation system for a high speed transport vehicle utilizing the interaction between superconducting magnets on the vehicle and an ensemble of normal metal loops and windings on a fixed guideway that is constructed along the ground.
2. Description of Related Art
With an increasing need for transportation systems that can minimize environmental and noise pollution, that are more energy efficient, and that can reduce the traffic congestion and improve travel safety, and with new advances in materials and technology, interest in passenger and freight ground vehicles levitated by magnetic forces has also grown. Such systems have been proven in pilot projects to be able to achieve speeds of 300 miles per hour and faster. At such high speeds, conventional wheeled vehicles become highly inefficient and impractical.
Vehicles that are levitated magnetically without contacting a support surface encounter reduced friction and vibration problems due to roadbed irregularities. Passenger and freight transport systems utilizing normal permanent magnets or electromagnets have utilized magnetic attraction or repulsion, with the carrier and track held at a set distance through feedback from a gap sensor. One such system, for example, provided for a row of vertical support magnets and another row of lateral guide magnets. In the event of failure of the magnetic levitation, some systems have also provided emergency gliding or set-down skids for a controlled crash. Normal motive systems, as well as linear induction motors have also been utilized with such systems for propulsion. However, normal magnetic levitation systems are typically massive, consume large amounts of energy to control, suspend, and propel the vehicle, and are constrained to have a small clearance, typically less than one inch between the suspended vehicle and the guideway.
Lighter, more energy efficient electromagnetic inductive levitation and stabilization systems that enable large clearances, typically several inches, have also been proposed for a ground vehicle, utilizing superconducting magnets carried by the vehicle. An early system provided for a train levitation system based on the magnetic repulsion generated between two superconducting loops carrying D.C. current, one on a moving train and one on a stationary track. In a subsequent system, the superconducting magnets interacted with a plurality of arrays of longitudinally extending shorted loops of a non-magnetic metal conductor, such as aluminum, in a guideway. The vehicle was suspended over the guideway by magnetic interaction of the superconducting magnets with the shorted loops in the guideway. The vehicle was supported on wheels when at rest, or when it was started, or operated at transitional speeds below that necessary to suspend the vehicle. Vertical lift was provided by magnetic interaction of the superconducting magnets with coils in the form of individual shorted loops. Horizontal stability was provided by magnetic interaction of the superconducting magnets with coils arranged in a figure 8 shape or in the form of a longitudinally extending series of two vertically spaced, electrically separated loops. The superconducting magnets were accommodated in a coolant container of a car of the train, and auxiliary and emergency support devices, such as wheels and a fixed skid, were provided support in the event that the levitation of the train was terminated in use, such as if the superconducting magnets became normal. The train was propelled by a linear synchronous motor, in which thrust was obtained by providing AC current to propulsion windings on the ground, which magnetically interacted with, and pushed forward the superconducting magnets located on the car of the train.
However, the guideways previously proposed for magnetically levitated vehicles are typically subject to accumulation of hazardous foreign material or objects, such as snow, ice, or other small, loose objects that can fall on or near the track. It would be desirable to provide for an electromagnetic induction levitation guideway that can readily shed such hazardous foreign material, and detect heavy foreign objects on or otherwise contacting the guideway. It would also be desirable to provide such a system for detecting not only foreign objects, but also for determining the location and speed of the vehicle travelling along such a guideway.
In addition, the guideways previously proposed for magnetically levitated vehicles do not readily permit controlled high speed mechanical braking in the event that the superconducting magnets were to fail. It would be desirable to provide such a guideway that incorporates a kinetic energy absorption system for maintaining the vehicle on the guideway and controlling a high speed emergency braking of the vehicle in the rare event of failure of the magnetic levitation of the vehicle.
Moreover, previously proposed magnetic levitation guideways have not been designed as lightweight pre-fabricated structures that can be mass produced in a factory, shipped by conventional methods such as by truck or rail, and erected in the field with minimum labor to produce the finished ready-to-operate system. Such a guideway would be highly desirable, because of the lower costs associated with factory mass production, and the faster, less disruptive erection of the guideway in the field.
Another deficiency of previously published magnetic levitation system designs has been their inability to change to different guideway configurations using the same magnetic arrangement on the vehicle. This ability would allow the use of a low cost guideway for the bulk of a maglev route, with a shift to a different guideway configuration when high speed switching or other special situations become necessary. The present invention can shift between a wide range of beam, channel, and planar guideway configurations without changing the magnet arrangement on the vehicle.
A further deficiency of previously published guideway designs is their lack of smooth, non-bumpy surfaces. This results in increased aerodynamic drag and noise when the air displaced by the high speed vehicle interacts aerodynamically and acoustically with the non-smooth surface. The shape and surface of the guideway in the present invention is designed to be free of periodic irregularities and structure so that the displaced air currents always interact with a constantly uniform smooth surface that generates a minimum of air drag and noise.
It would also be desirable for a guideway for a vehicle levitated by superconducting magnets to be configured to allow the electromagnetic induction levitation system and the linear synchronous motor windings to consume a relatively low amount of energy, particularly compared to other conventional forms of transportation.
The present invention meets the needs described above.